1. Field of the Invention
The present invention relates to a manufacturing method for supermicro-connectors capable of connecting electrodes of semiconductor chips and circuit boards electrically to one another with high reliability.
2. Description of the Related Art
Semiconductor chips are formed each with a large number of electrodes arranged at fine pitches. With the progress of high-integration versions of circuits, the number of electrodes used in each chip is increasing steadily. Dual in-line packages (DIPs) which use lead frames had been prevalent means for electrical connection between the electrodes of the semiconductor chips and external equipment. As the electrodes of each chip increased in number and came to require latticed or multilayer arrangement, however, the conventional DIPs of the lead-frame type ceased to be effective connecting means.
In the case where a large number of electrodes are used in each semiconductor chip, therefore, the bare chip packaging method (also referred to as chip-on-board method or flip chip method) is employed. According to this method, the electrodes of each semiconductor chip and electrodes of a circuit board, which are as many as those of the chip and are arranged at pitches equal to the arrangement pitches of the chip electrodes, are connected by reflow soldering using solder balls, whereby the semiconductor chip is mounted directly on the circuit board.
In this bare chip packaging method, however, the electrodes of the semiconductor chip and the circuit board are connected directly to one another by means of the solder balls. As the temperature rises during use, therefore, the circuit board, having the semiconductor chip mounted directly thereon by this method, is subjected to thermal strain which is attributable to the difference in thermal expansion between the chip and the board. This thermal strain would be concentrated on soldered regions to damage them, thereby causing connection failure.